Vanilla buttercream frosting

The frosting can be refrigerated in an airtight container for up to 3 days. Before using, bring to room temperature; beat with the paddle attachment on medium-low speed until smooth.

1π cups sugar

1 vanilla bean, halved lengthwise

7 large egg whites

Pinch of salt

1 1/4 pounds (5 sticks) unsalted butter, cut into tablespoon-size pieces, softened

2 teaspoons pure vanilla extract

• Put the sugar in the bowl of a food processor, and scrape in the vanilla seeds. Process until combined. Sift into a bowl, and discard any large pieces of vanilla.
• Put the egg whites, vanilla-sugar mixture, and salt in the heatproof bowl of an electric mixer. Set over a pan of simmering water. Whisk constantly until the sugar has dissolved and the mixture registers 160F on an instant-read thermometer.
• Return the bowl to the mixer; fit the mixer with the whisk attachment. Beat on medium-high speed until stiff, glossy peaks form and the mixture is cool, about 10 minutes.
• Switch to the paddle attachment. With the mixer on medium speed, add the butter, 1 or 2 tablespoons at a time, mixing well after each addition. Mix, scraping down the sides of the bowl as needed, until the mixture is smooth. Mix in the vanilla extract. Use immediately, or cover and refrigerate.

MAKES ABOUT 6 CUPS